Myocardial gene therapy can be used for the treatment of a number of cardiovascular diseases, including ischemic cardiomyopathies, congestive heart failure, and malignant arrhythmias (Nabel (1995) Circulation 91:541–548). A useful vector for myocardial gene delivery will allow efficient and stable transduction of cardiomyocytes with a variety of transgenes after either direct intramyocardial injection or infusion into the coronary arteries or sinuses. For example, plasmid DNA vectors injected directly into the left ventricular myocardium have been expressed for ≧6 months by cardiomyocytes adjacent to the area of injection (Lin et al. (1990a) Circulation 82:2217–2221; Kass et al. (1993) Proc. Natl. Acad. Sci. USA 90:11498–11502; and Guzman et al. (1993) Circ. Res. 73: 1202–1207). However, the therapeutic usefulness of this approach has been limited by the low efficiency of cardiomyocyte transduction (0.1% to 1.0% of cardiomyocytes in the area of injection).
Both intramyocardial injection and intracoronary infusion of replication-defective adenovirus (RDAd) vectors have been used to efficiently transduce cardiomyocytes in rodents, rabbits, and pigs in vivo. However, the feasibility of adenovirus-mediated gene transfer has been limited by immune responses to viral and foreign transgene proteins, which cause significant myocardial inflammation, eliminate virus-transduced cells within 30 days of infection, and thereby result in transient recombinant gene expression in immunocompetent hosts (Guzman et al. (1993) Circ. Res.73:1202–1207; French et al.(1994) Circulation 90:2414–2424; and Barr et al.(1994) Gene Ther. 1:51–58).
Recently, rAAV vectors have been shown to program efficient and stable recombinant gene expression in skeletal muscle and liver in both rodents and primates (Fisher et al.(1997) Nat. Med. 3:306–312; Kessler et al. (1996) Proc. Natl. Acad. Sci. USA 93:14082–14087; and Snyder et al. (1997) Nat. Genet. 16: 270–276) and in cardiac muscle directly injected with rAAV (U.S. Pat. No. 5,858,351 to Podsakoff et al.). However, since rAAV vectors used in gene therapy applications, unlike RDAd, do not encode viral proteins, the rAAV vectors have not been associated with immune responses to foreign transgene proteins.
While a previous report showed that rAAV can transduce cardiomyocytes in vivo, the efficiency of rAAV-mediated transgene expression in the heart was both low (about 0.2%) and localized (Kaplitt et al. (1996) Ann. Thorac. Surg. 62:1669–1676). In that study, pigs hearts were rapidly perfused with a low titer of rAAV (less than 104 expressing units AAV per gram of body weight). Based on those results, infusing rAAV into the heart would have severely limited use as a vector for myocardial gene therapy. However, as demonstrated herein, this invention establishes that by infusing rAAV in much higher amounts proportional to body weight of the animal and for particular time periods, then rAAV provides unexpected efficient and stable gene transfer into the heart, opening up use of rAAV vectors to deliver therapeutically-effective molecules to cardiomyocytes in amounts useful for treating or ameliorating cardiac diseases or conditions.